This invention is generally in the field of capillary electrophoresis, and particularly to apparatus and method for optimizing the results of a parallel capillary electrophoresis operation.
Capillary electrophoresis (CE) is a chemical separation technique originally involving the use of a single capillary and more recently involving the use of multiple parallel capillaries, referred to as parallel capillary electrophoresis. Parallel CE is growing in popularity since this technology allows multiple samples to be analyzed quickly, efficiently and simultaneously. This is particularly advantageous in combinatorial chemistry where many hundreds and even thousands of samples are analyzed over a short period of time. Parallel CE involves the use of a xe2x80x9cbundlexe2x80x9d of capillary tubes, e.g., 96 tubes arranged side by side in an array. A chemical sample to be analyzed is placed in each tube, and a high voltage is applied to the tube, causing the components of the sample to migrate in the tube at different speeds, thereby causing separation of the components which can then be analyzed by conventional light absorption or other techniques. In one such technique light emitted from a light source is passed through capillary tubes containing samples to be analyzed. Light transmitted through the tubes is imaged by a lens on a linear array of photodiodes, the outputs of which are connected to conventional signal processing circuitry which is used to compute and analyze the light absorbence of the samples. An electropherogram, i.e., the plot of light intensity (absorbence) versus time is typically displayed on a computer screen and/or printed out for evaluation. Reference may be made to the following patents and publications for a more detailed description of CE, including parallel CE, and various analytical techniques used in CE, including the light absorption technique referred to above: U.S. Pat. Nos. 5,900,934, 5,324,401, 5,312,535, 5,303,021, 5,239,360; C. Culbertson et al., Analytical Chemistry, 70, 2629-2638 (1998); and X. Gong et al., Analytical Chemistry, 71(21), 4989-4996 (1999).
Among the several objects of this invention may be noted the provision of apparatus and method for optimizing the results of a capillary electrophoresis operation, particularly the clarity, resolution and/or detection limits of electropherograms generated during the operation; the provision of such apparatus and method which involve the use of conventional components for reduced cost; and the provision of such apparatus and method which are quick and easy to use.
In general, this invention is useful in a parallel capillary electrophoresis system for separating and analyzing the components of multiple chemical samples. The system comprises a bundle of capillary tubes arrayed to have at least portions of the tubes extending generally parallel to one another in a first plane, each tube being adapted for the flow of a chemical sample therethrough, a light source for emitting light to pass through said capillary tube portions, and a photodetector comprising a linear array of photodetector elements for receiving light passing through the capillary tubes. The improvement of this invention comprises a photodetector mount mounting the photodetector for rotation about an axis extending generally perpendicular to the aforesaid first plane whereby the angular position of the linear array of photodetector elements can be adjusted to an optimal position for analyzing the light passing through the capillary tube portions.
This invention is also directed to the photodetector mount separate and apart from the CE system described above. In this aspect, the mount comprises a stationary member having an opening therein, a rotatable member mounted on the stationary member for rotation on an axis relative to the stationary member, and means for attaching the photodetector to the rotatable member for rotation with the rotatable member whereby the angular position of said linear array of photodetector elements can be adjusted to an optimal position for analyzing the light passing through the capillary tube portions.
This invention is also directed to a method comprising the steps of mounting the photodetector on a stationary surface for rotation about an axis extending generally perpendicular to the aforesaid first and second planes, and rotating the photodetector on said axis to a position in which the linear array of photodetector elements is at a selected angle relative to a projected image of the capillary tube portions.
Other objects and features will be in part apparent and in part pointed out hereinafter.